Science

Supernova study questions cosmic acceleration, prompting scientific debate

A study suggests cosmic expansion may be slowing, though other researchers dispute the claim, according to ScienceDaily.

Updated Sep 10, 2026 · 07:47 UTC1 reports

The short version

Researchers from the Tata Institute of Fundamental Research and the University of Oxford reanalyzed more than 1,700 Type Ia supernovae and argue cosmic expansion may be decelerating.[ScienceDaily]
The authors claim that failing to adjust for the age of progenitor stars creates the false impression that expansion is accelerating.[ScienceDaily]
Other cosmologists dispute the findings, with a contemporaneous paper maintaining that observations still support an accelerating universe.[ScienceDaily]
Upcoming observations from the Rubin Observatory are expected to test both positions with data from hundreds of thousands of supernovae.[ScienceDaily]

Researchers at the Tata Institute of Fundamental Research and the University of Oxford examined more than 1,700 Type Ia supernovae from the Pantheon+ dataset.[ScienceDaily]
The researchers argue in Monthly Notices of the Royal Astronomical Society that the universe's expansion may be slowing rather than speeding up.[ScienceDaily]
Professor Subir Sarkar stated that uncorrected stellar age variations in supernovae can lead to false conclusions about cosmic acceleration.[ScienceDaily]
A separate study co-authored by Professor Maria Vincenzi in the same journal issue disputes the revision and finds observations still favor acceleration.[ScienceDaily]
The Rubin Observatory's Legacy Survey of Space and Time is expected to observe hundreds of thousands of supernovae to help resolve the dispute.[ScienceDaily]

Whether the rate of cosmic expansion is accelerating or decelerating remains contested among cosmologists evaluating supernova data.[ScienceDaily]

Outlet counts describe coverage, not independent confirmation. Reports may share a wire service or original source.